Casing for multi-stage centrifugal pump



Jan. 2, 1968 s. MDGYESY l 3,361,013

CASING FOR MULTI-STAGE CENTRIFUGAL `PUMP Filed oct. 22, 1965 Y 2 sheets-sheet '1 Stephen Medgyesy BY 4 M7 ,d l mw @av am-l/rlff 1,

TToRNEYs Jan. 2, 1968A s.' MEDGYEsY l CASING FOR MULTISTAG GENTRIFUGAL PUMP 2 sheets-sheer 2 Filed. oot, 22,` 1965 United States Patent Oiice 3,361,073 CASING FOR MULTI-STAGE CENTRIFUGAL PUMP Stephen Medgyesy, Etfretikon, Zurich, Switzerland, assignor to Sulzer Brothers Limited, Winterthur, Switzerland, a Swiss company Filed Oct. 22, 1965, Ser. No. 500,805 Claims priority, application Switzerland, Oct. 30, 1964, 14,119/64 4 Claims. (Cl. 103-108) ABSTRACT F THE DISCLOSURE There is disclosed a casing for a multi-stage centrifugal pump comprising a plurality of annular sections which are joined together in coaxial relation into a unitary casing. The sections thus joined together are bounded at the radially inner limit thereof by a cylindrical surface, and each pair of adjacent sections defines an annular space open at that cylindrical surface toward the axis of the casing and bounded at the radially outer limit thereof by portions of two axially adjacent sections of the casing. The casing further comprises in each of these annular spaces a flow-reversing assembly comprising a ring and a plurality of vanes afiixed thereto, the assembly being split into a plurality of sections divided from each other along surfaces parallel to a common radius from the axis of the casing to permit installation and withdrawal of these assemblies without disassembly of the outer portions of the casing.

The present invention pertains to centrifugal pumps and more particularly to a casing for a multi-stage pump. The casing of the invention includes at least one flowreversing assembly between two adjacent stages of the pump, this assembly having flow channels in which the fluid being pumped, which is forced centrifugally outward by the impeller of one stage of the pump, is reversed and is fed centripetally to the impeller of the next stage. Inv

accordance with the invention, the casing is made up of plural sections which are fastened together but which are divided from each other at the location of the interstage ow direction reversing assembly, and this assembly includes a ring having flow channel-defining blades or vanes attached thereto. These blades serve to reverse the direction of flow of the duid being pumped and they serve also to support the reversing assembly from the wall of the casing.

In centrifugal pumps having plural stages, the Ifluid driven through one stage is delivered thereby to a diffuser, and is thereafter deflected from the direction radially out ward from the axis of the pump and reversed, to be delivered toward the axis and to the impeller of the next stage. Since the vanes necessary for this purpose are of complicated shape and diliicult to construct, it is customary to separate the diffuser vanes, which extend approximately perpendicularly to the axis, from the reversing section as such and to build the latter separately. In this way there is obtained a casing having an inner cylindrical bore into which on assembly the irnpellers and diffuser or diffusers may be inserted axially. Although this form is somewhat easier to manufacture, nevertheless there remain substantial difficulties in the construction of the pump casing itself, particularly with respect to the reversing channels which must be provided therein. The invention has for an object the provision of a form of construction in which it is not only easier to construct the pump casing but in which additionally the channels of the reversing section are readily removed from the casing, e.g., for replacement or repair.

The invention will now be further described with reference to the accompanying drawings, in which:

FIG. l is an axial section through a pump according to the invention;

FIG. 2 is a fragmentary axial section of the casing of the pump of FIG. l;

FIG. 3 is a section taken on the line III-III of FIG. 2; and

FIG. 4 is a partial developed view of one of the guides or flow-reversing assemblies of the pump of FIGS. 1-3, seen perpendicularly to the axis and from the radially outer side of that assembly.

The centrifugal pump of FIG. l comprises a casing made up of annular sections 1, 2 and 3, which may be welded together. The sections 1, 2 and 3 together constitute an annular structure in which are provided reversing assemblies generally indicated at 4. The casing sections 1, 2 and 3 define, at their radially innermost limits, a common cylindrical surface whose trace in the plane of FIG. 2 is indicated at 25, of radius r1 from the pump axis 26, in which the casing sections 1, 2 and 3 are themselves coaxial. Each of the assemblies 4 comprises a ring 4a and blades or vanes 4b (see FIG. 4). The pump casing is provided with a cover 5 at the outlet or high pressure end thereof and With a closure 6 at the suction or inlet end thereof. A shaft 7 is borne in the parts 5 and 6 and this shaft supports the impellers or blade wheels 8, 9 and 10 of the individual stages with their appurtenant seals. The pump additionally includes ring-shaped assemblies of diffuser elements or vanes 11, 12 and 13, and assemblies of supplementary diffuser elements 14 and 15, all of which are introduced into the casing and fastened therein. The diffuser vanes rest against a thrust ring 16 which is seated in a groove of the casing. The ring 16 bears the axial thrust of the pump. On the side of ring 16 remote from the diffuser elements 12, two rings 17 and 18 bear against the thrust ring 16. These rings 17 and 18 are arranged to be forced apart by means not shown, such as screws or wedges, so as to press the diffuser elements of the adjacent pump stage against the next thrust ring, or in the example shown, against a projection 19 of the casing.

FIG. 2 illustrates for clarity the casing of the pump of FIG. 1 alone. As can be seen from this figure, the sections 1 and 2 of the casing are joined together by means of a rcircumferential weld seam 30, and the sections 2 and 3 are similarly joined by means of a Weld seam 31. In each case, the two parts so joined define in the vicinity of their junction an annular hollow space of inner and outer radial limits r1 and r2 in FIG. 2, into which there is introduced the assembly 4 with its ring 4a and blades 4b, the blades bearing against the wall of the casing. The annular space in which the reversing assembly 4 is received is thus open at its radially inner limit, at the surface 2S, and is bounded at its radially outer limit by surfaces 2a and 3a on portions of the casing sections 2 and 3 adjacent their junction at 31. The blades 4b may, if desired, be secured to the housing by spot welds at selected points as indicated at 32 and 33.

FIG. 3 shows a sectional view taken on the line III-III in FIG. 2. In FIG. 3, the reversing vane assembly between casing sections 2 and 3 and generally indicated at 4 in FIG. 2, and which comprises a ring 4a and stator blades 4b, is shown as made up of four parts or subassemblies 24a, 2412, 24C and 24d which join together along two planes M and N parallel to the axis of the pump. It is to be noted that the sections 1, 2 and 3 of the casing are not split along these planes. When the shaft, impellers and other parts of the pump radially inside the surface 25 have been Withdrawn, in accordance with the showing of FIGS. 2 and 3, the four parts 24a, 24b, 24e and 24d may be withdrawn from the annular space between radial limits 1'1 and r2 above described and in which the reversing assembly belongs, by motions toward the axis in the directions indicated by the arrows in FIG. 3, Conversely, they may be reintroduced into proper position by motions in the opposite direction. More generally stated, at least one of the pieces lor sections of which the assembly 4 is lmade up is divided from the other sections of that assembly by surfaces parallel to a common radius from the axis of symmetry 26 of the casing, so as to permit withdrawal of that section toward that axis. It will be observed in FlG. 3 that the portions of planes M and N which bound the subassembly 24d are parallel to a common radius from axis 26.

FIG. 4 shows a partial development of one reversing assembly. The blades 4b are shown schematically only. In actuality, the guide channels defined by the blades are of more complicated shape since account must be taken not only of the direction of flow lof the liquid but also of the changing velocity thereof and hence of the correspondingly changing cross-section of the channels.

By means of the invention, there is achieved a simplified construction of the pump casing and reversing channels. The parts of the casing take simple shapes lwhich can be readily manufactured by casting. The reversing assembly of the invention is a simple ring having open channels whose construction likewise does not present difficulties. The casing of the invention is light in weight and the amount fof material required therefor is small by comparison with known forms of pump casing construction.

The other reversing assemblies, such as that between the casing sections 1 and 2, possess the same properties as have hereinabove been described for the reversing assembly between casing sections 2 and 3.

Additionally, the casing of the invention permits simple assembly and disassembly of the reversing assemblies for change or repair thereof. If those assemblies are made up in sections as shown in FIG. 3, these can readily be mounted in a pump casing and welded together and, according to circumstances, readily removed therefrom. IIt is suicient to this end to grind out or otherwise open the welds 32 and 33, which need not be long and in fact need be provided only at a few places around the pump axis. If it is additionally desired to provide for simple replacement, the reversing assemblies 4 may be otherwise fastened into the casing, as for example by means of pins disposed in the casing at one or more points around the circumference thereof, to secure those assemblies against rotation. The casing elements 1, 2 and 3 may likewise be joined together by means other than the welding shown. Thus, for example, it is possible to provide a construction in which the casing elements are provided with franges by means of which they are fastened together with the help of screws.

The term multi-stage as used herein is to be understood as including centrifugal pumps with two or any larger number of stages.

I claim:

1. A casing for a multi-stage centrifugal pump having a central axis, said casing comprising a plurality of annular sections joined together in coaxial relation into a unitary casing, a pair of said sections being provided with annular radially extending axially spaced projections dening an annular space therebetween, and said space being open toward the axis of the casing, a separate flow reversing assembly disposed in said space, said assembly including a ring intermediate said projections, a plurality of blades secured to said ring and engaging the wall defining said annular space.

2. A casing according to claim 1 wherein said assembly is composed of demountable sections insertable into said annular space from the axis in which said annular sections are coaxial.

3. A casing according to claim 1 wherein said assembly is composed of sections at least one of which is divided from other sections of said assembly by surfaces parallel to a common radius from the axis in which said annular sections are coaxial.

4. A casing according to claim 1 wherein said assembly is composed of plural sections divided from each other along planes parallel to each other and to the axis in which said annular sections are coaxial.

References Cited FOREIGN PATENTS 411,913 1910 France.

25,391 1905 Great Britain.

563,532 8/1944 Great Britain.

221,3 87 8/ 1942 Switzerland.

HENRY F. RADUAZO, Primary Examiner. 

